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Whispering Gallery Detects and Sizes Smallest Virus


A rendering of the whispering gallery mode sensor. Courtesy of Stephen Holler

A Fordham physics professor and his research collaborators at The Polytechnic Institute of New York University and City University of New York have created new nanotechnology to detect the world’s smallest known aqueous-borne virus.

Stephen Holler, Ph.D., and the researchers created a “plasmonic hybrid whispering gallery mode sensor,” which consists of a microscopic glass bead no wider than the thickness of a human hair (approximately 100 microns in diameter.) The bead has a single nanoscopic antenna affixed to it that–with the aid of light forces–can draw a single virus particle to a nanoplasmonic “hot spot.” Using a wavelength tunable laser source, the team then interprets the shifts in colors of light (i.e. resonances) that circumnavigate the glass bead, to detect and measure the size of the attracted virus–in this instance an RNA virus whose molecular weight is less than all known viruses.

Such direct object detection of a single bio-nano-particle of this size had previously been unattainable, said Holler.

This record-setting achievement was published in the July 30 issue of Applied Physics Letters, and subsequently highlighted by the American Institute of Physics.

Holler said the new discovery has numerous useful applications for identifying and studying biological particles, but more importantly for real-time medical diagnostics.

“Having achieved a detection limit below all known virus particle sizes means that medical diagnostic technology may soon be capable of rapidly detecting the presence of a single virion in blood or saliva – including common viruses such as influenza, HIV, Hepatitis and West Nile,” he said. “We envision doctors performing these tests in the office and getting results in minutes, not the days necessary for current blood tests. Early detection means immediate treatment, which can save lives.

“In addition, this sensor platform can serve as a sensitive device for monitoring for the presence of other biological and non-biological targets for medical (e.g., bacterial infection) and security applications (e.g., detection of biological or chemical warfare agents, explosives, and radiological/nuclear contamination).”

The researchers hope to soon push the detection limits further, and achieve single protein detection and characterization.


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